Home base station is a small and low-power base station deployed in indoor places such as family and office, mainly to provide users with higher service rate, reduce the fund required for the high-rate services, and compensate for insufficient coverage of existing distributed cellular wireless communication systems. The advantages of the home base station are cheap, convenient, low power output, plug and play, broadband access, using single-mode terminals and so on.
The home base station may be applied in the 3rd Generation (3G) or Long Term Evolution (LTE) mobile communication networks. The home base station is called home node B (HNB) for short when applied in the 3G network or Home Evolved NodeB (HeNB) for short when applied in the LTE network. For facilitating management of the home base station, a new network element, i.e., home base station gateway, is introduced in the radio access network. The home base station gateway mainly functions to validate the security of home base station, process the registration of home base station, maintain and manage the operation of home base station, configure and control home base station according to the requirements of operators, and exchange data between a core network and the home base station. FIG. 1 is a diagram illustrating the network architecture of a 3G home base station, in which the 3G Home Base Station (HNB) is connected to a Home Base Station Gateway (HNB GW) through a newly defined luh interface. The home base station gateway provides luPS and luCs interfaces to the packet switched and circuit switched domains of a core network. It is mandatory for the 3G network to be deployed with the home base station gateway for shielding the impact on User Equipment (UE) and network side after the introduction of home base station. However, it is optional for the LTE network to be deployed with the home base station gateway, so two connections exist for home base station and core network in the LTE network: direct connection from the home base station to the core network element, and connection from the home base station to the core network element through a gateway, as shown in FIGS. 2 and 3. For the scenario in FIG. 3 of introducing a home base station, the home base station might not be integrated with the functions of user interface, and the user interface is directly established between the home base station and the user interface gateway of the core network, thereby flattening the user interface and reducing the delay of data transmission, as shown in FIG. 4.
In FIG. 1, the packet switched domain includes a Service GPRS Support Node (SGSN) and a Gateway GPRS Support Node (GGSN).
In FIGS. 2 to 4, the core network gateway is also called user interface gateway, i.e., System Architecture Evolution Gateway (SAE-GW), including a Serving Gateway (S-GW) and a Packet Data Network Gateway (P-GW).
Closed Subscriber Group (CSG) is a concept introduced after the introduction of home base station. Generally, the subscribers in a family or an enterprise form a CSG identified by a CSG ID. The home base stations serving the subscribers in the CSG have the same CSG ID. The subscribers can access many home base stations corresponding to multiple CSGs, such as office and home thereof, by subscribing to operators. Therefore, the concept of allowed CSG list is introduced and saved in the home subscriber data servers at UE and network sides. For the LTE, the home subscriber data servers of network are Home Subscriber Server (HSS) and for 3G networks, the home subscriber data servers of network are Home Location Register (HLR). The UE selects radio cells mainly by the list, and the home base station notifies the UE of the CSG ID and usage mode thereof through broadcast. After obtaining a broadcast message, if it is found that the base station is in the closed usage mode and the CSG ID is not in the allowed CSG list saved thereby, the UE believes that the cell of the home base station is not suitable for access and automatically selects other cells suitable for access, so as to avoid frequent access attempts, thereby reducing the consumption of battery and air interface resources. When the UE initializes the access, the home subscriber data server at the network side sends the allowed CSG list subscribed to by a subscriber to a mobility management unit of the core network. The mobility management unit of the core network performs access control to the UE using the list. For the 3G network, the mobility management unit is an SGSN. And for the LTE network, the mobility management unit is a Mobility Management Entity (MME). If the UE accesses the core network through an unauthorized CSG-mode home base station, the core network will reject the access of such UE. The home base station may also be used as a general base station. Then, at this moment, the access mode of the home base station is the open mode. In this mode, the home base station may be accessed by any UE. The UE accessed in such mode will not be subjected to the access control by the mobility management unit. Likewise, the home base station can be in a hybrid mode, namely, some UEs adopting the CSG-mode access, and some UEs adopting the open mode access.
When a UE is idle, the air interface connection between the UE and the base station is released, and if there are external data required to be sent to the UE through a network, an MME/SGSN needs to inform the base station in the Tracking Area (TA) list where the UE is located to page the UE, so as to inform the UE to establish an air interface connection. And when the home base station gateway is available, the MME/SGSN needs to inform the home base station gateway that informs the base station to page the UE. According to different network architectures, when an MMS is directly connected to a home base station, the MME learns the access mode of the home base station. And when the MME/SGSN is connected to the home base station through a home base station gateway, the MME/SGSN does not learn the access mode of the home base station, which mode is only known by the home base station gateway.
In the scenario where the home base station is directly connected to the MME, in order to reduce the resource waste caused by paging, it is possible to use the paging optimization, that is to say, for the CSG-mode home base station, it is not required to inform the CSG-mode home base station to page the unauthorized UE. Namely, not paging such base station whose cell is the CSG-mode CSG cell, and the UE does not subscribe to the CSG of the CSG cell. Herein, the base station is called the CSG-mode home base station that does not authorize the UE. When a home base station is connected to an MME/SGSN through a Home Base Station Gateway (HeNB GW/HNB GW), the MME/SGSN will send a paging message including an allowed CSG list of a UE to the home base station gateway, and the home base station gateway determines to use the paging optimization. That is to say, for the CSG-mode home base station, it is not necessary to inform it to page the unauthorized UEs.
For the subscribers using the emergency service, a home base station providing such service may be accessed. At this point, two scenarios are available.
1. A UE is normally attached to a network under a base station in normal service, and then establishes an emergency service. After completion of the emergency service, the UE enters into an idle state and moves under a closed home base station. The CSG ID of the closed home base station is not in the allowed CSG list of the UE, but, in a broadcast message, the home base station indicates that it may provide the emergency service, so that the UE opts for residing in the CSG cell.
2. A UE is started under a closed home base station. The CSG ID of the closed home base station is not in the allowed CSG list of the UE, but, in a broadcast message, the home base station indicates that it can provide the emergency service, so that the UE initializes an emergency attachment to a network, after which the UE enters the idle state.
In the two scenarios above, the UE having the emergency service may reside in the unauthorized CSG-mode home base station. The MME/SGSN or Home Base Station Gateway (HeNB GW/HNB GW) will not be informed to page the UE according to the paging optimization of the prior art, such that the UE cannot be paged, and communication failure occurs.